The present invention pertains generally to sight glass assemblies and, more particularly, to low cost modular sight glass assemblies which are suitable for installation where vapor control is required.
Sight glass assemblies are widely used in many different types of machines and vessels to observe internal workings. For many installations, the sight glass window and the surrounding framework must be appropriately engineered to withstand and contain the internal environment. This can require a complex assembly of parts, including bezels with multiple interfacing components, and glass or transparent layers with highly engineered interfaces between the glass and the bezel housing. For example, U.S. Pat. Nos. 3,941,460; 3,977,251; 4,169,309; 4,182,179; 4,206,537; 4,436,375; 4,468,095; 5,210,658 and 5,763,776 all disclose complex sight glass assemblies with heavy machined frame structures secured about a glass piece and attached to a vessel in high pressure or corrosive environments. These types of assemblies are of course costly to produce, assemble and install, and are therefore generally found on specialized industrial equipment, such as chemical and food processing equipment. Because it is critical in these applications to maintain the view path for inspection of internal conditions, these types of highly engineered sight glass assemblies are justified.
In other applications, the environment may be less hostile or corrosive, allowing for a less complex construction. For example, U.S. Pat. No. 5,735,168 discloses a sight glass assembly for use on an animal feeder that does not require access to the interior, but which contains multiple layers and at least four fasteners for attachment to a wall. In other words, the design and construction of a sight glass assembly is highly dependent upon the installation environment.
The development of new type of water heater has created a new application for an effective yet economical sight glass assembly. Until recently water heaters have been manufactured with the pilot light and burner contained in a open air shroud underneath the water tank. This allows flammable vapors to easily come into contact with the open flame of the pilot or burner and cause an uncontrolled explosion or fire. To prevent this, a vapor-controlled flame chamber has been developed for use with a water heater. As described for example by U.S. Pat. No. 6,116,195, an enclosed flame trap assembly for water heaters has an air inlet in the form of a plate with a plurality of ports, each port being sized and shaped to cause air and extraneous fumes to pass through the ports at a velocity higher than the flame velocity of the extraneous fumes, to confine ignition and combustion of extraneous fumes within the combustion chamber. More specifically, the patent describes the exact design of openings or xe2x80x9cportsxe2x80x9d in the air inlet which inhibit flames from ignition of extraneous fumes from exiting the flame trap assembly. This greatly reduces the risk of accidental home fires caused by flammable vapors coming into contact with the flame of the water heater burner. This innovation has been heralded as a significant safety improvement in water heater home safety by the U.S. Consumer Product Safety Commission. The flame trap assembly however, is otherwise substantially sealed, which interferes with inspection of the pilot and burner flame.
Thus the need is created to incorporate a sight glass into this type of flame trap assembly to enable visual inspection of the burner assembly and operation, particularly with respect to gas flow in the absence of a flame, which could lead to gas poisoning or uncontrolled explosion.
This type of sight glass is primarily subject to heat, rather than pressure. Otherwise, the primary performance criteria (in addition to providing the view path) is to maintain the vapor control integrity of the flame trap assembly. Therefore, a principal objective of the invention is to provide a sight glass assembly which maintains the vapor control function of the flame trap assembly but which is economical for mass production in flame trap equipped water heaters.
The present invention provides novel solutions to these and other aspects of water heater flame control systems, by providing a modular sight glass assembly frame that does not require custom fasteners or fittings, but still creates a sufficient seal and window area. The design is also economical to produce and assemble. In one embodiment the securing tabs allow for the sight glass assembly to be easily snapped into position on the exterior of the flame trap compartment. In another, the sight glass assembly is secured by two rivet-like fasteners, allowing for a more flexible placement and less cutout area in the flame trap assembly compartment wall.
In accordance with one general aspect of the invention, there is provided a sight glass assembly with frame casing having a front face, side walls, an upper wall, a lower wall, an opening in the front face, and securment extensions which extend from at least two of the side walls; a piece of planar transparent material having an outer perimeter dimensioned to fit within the walls of the frame, and to span the opening in the front face, wherein the walls extend over the edges of the transparent material; a generally planar gasket having an outer perimeter greater than an outer perimeter of the casing, and an opening having a perimeter less than the outer perimeter of the transparent material wherein the securement extensions are configured to engage with a structure having an opening generally aligned with the openings in the gasket and the frame to provide a sight glass through the opening in the structure.
In accordance with another general aspect of the invention, there is provided a modular sealed sight glass assembly adapted for attachment to a wall section to provide a sealed view path, including a frame having a planar face wall and an opening in the face wall defining a viewing port; framing walls extending generally perpendicularly from a perimeter of the face wall, at least one of the framing walls further comprising a securement extension; a piece of transparent material dimensioned to fit within the framing walls and against the face wall; a gasket having an outer perimeter greater than the face wall of the frame, and an internal opening having a perimeter less than a perimeter of the piece of transparent material, the internal opening of the gasket being generally aligned with the opening in the face wall, and the gasket being positioned against the transparent material opposite to the face wall of the frame.
And in accordance with another aspect of the invention, there is provided a sight glass assembly in combination with a combustion chamber, the combustion chamber having a shroud with at least one wall and an opening through a cross-section of the shroud wall, a sight glass frame having a face plate with an opening and perimeter walls which extend perpendicularly from the face plate, a planar transparent piece which fits within the perimeter walls of the frame and against the face plate, and a gasket with an opening which corresponds to the opening in the face plate and the opening in the shroud wall and which extends at least partially beyond a perimeter of the face plate, the gasket being positioned against the shroud wall and about the opening in the shroud wall, and the transparent material and face plate being positioned over the gasket and attached to the shroud wall.
These and other aspects of the invention are herein described with reference to the accompanying Figures representative of several of many possible embodiments of the principles and concepts of the invention.